Controlled tension web winding apparatus

ABSTRACT

Web winding apparatus in which a web of flexible material is adapted to successively pass over a first idler roll, under a dancer roll, over a second idler roll, over a lay-on roll and then be wound on a wind-up roll. The dancer roll is movable bodily through the medium of a first pair of arms which are pivotal about a first axis and the lay-on roll is movable bodily through the medium of a second pair of arms which are pivotal about a second axis. A mechanism, including a cam and a variable fluid pressure system, is connected to both pairs of arms and is so constructed and arranged as to effect application of programmed tension to the web by the dancer roll in response to bodily movement of the lay-on roll about the second axis during winding of the web on the wind-up roll.

United States Patent Saunders 1 1 Mar. 21, 1972 [s41 CONTROLLED TENSION WEB WINDING APPARATUS [72] Inventor:

[73] Assignee:

[22] Filed:

Alan J. Saunders, Somerville, NJ. Egan Machinery Company May 7, 1970 [21] Appl. No.: 35,326

[58] Field of Search [52] US. Cl ..242/75.3, 242/75.5,,242/75.5 l 242/75.53 [51] Int. Cl ..1 ..B65h 59/38 References Cited FOREIGN PATENTS 0R APPLICATIONS Germany ..242/75.5l

509,544 7/1939 Great Britain..... 1,037,727 8/1966 ..242/75 .51 Great Britain ..242/75.45

Primary ExaminerStanley N. Gilreath Assistant Examiner-Edward J. McCarthy Att0rney-F. J. Pisarra [57] ABSTRACT Web winding apparatus in which a web of flexible material is adapted to successively pass over a first idler roll, under a dancer roll, over a second idler roll, over a lay-on roll and then be wound on a windup roll. The dancer roll is movable bodily through the medium of a first pair of arms which are pivotal about a first axis and the lay-On roll is movable bodily through the medium of a second pair of arms which are pivotal about a second axis. A mechanism, including a cam and a variable fluid pressure system, is connected to both pairs of arms and is so constructed and arranged as to effect application of programmed tension to the web by the dancer roll in response to bodily movement of the lay-On roll about the second axis during winding Of the web on the wind-up roll.

12 Claims, 3 Drawing Figures PATENTEDMARZI I972 SHEET 1 OF 2 INVENTOR.

ALAN J. SAUNDERS ATTORNEY PATENTEDMARZ] I972 3,650,490

SHEET 2' [IF 2 INVENTOR.

ALAN J. SAUNDERS BY FIG. 3 7 W ATTORNEY 1 CONTROLLED TENSION WEB WINDING APPARATUS BACKGROUND OF THE INVENTION In the course of winding a web of a flexible material, such as paper, plastic film or the like, onto a windup roll, it is important to control the tension of the web. The reason for this is that, as the diameter of the wound web material on the windup roll increases, the peripheral speed increases at constant rotational speed, thereby progressively and objectionably increasing the tension in the web.

It is well known in the art that web winding may be accomplished by various types of winder drives, including drives which provide constant tension in the web throughout the winding cycle, drives which provide constant torque to the winder shaft and the web tension decreases in proportion to the increase in diameter of the windup roll, and drives which provide for a gradual decrease in web tension, commonly referred to as taper tension," somewhere between those of the first two types of drives.

One category of present day winder drives. is that known as the dancer roll controlled system in which a dancer roll ap plies a force upon a loop of a running web and creates tension in the web which is proportional to such force. By utilizing theposition of the dancer roll to actuate a transducer device, the winder drive can be controlled to obtaina windup roll rotational speed which will maintain the position of the dancer roll within a selected range of travel between stops. The indicated arrangement provides constant web tension throughout the winding cycle. With the view of modifying this system to effect decreasing tension in a running web, a number of developments have been made over the years. Such developments are exemplified by Hill U.S. Pat. No. 2,886,257, Haley U.S. Pat. No. 3,189,295 and Hank U.S. Pat. No. 3,317,156. The Hill tension control device utilizes a container having a supply of liquid and carried by a dancer roll assembly. The container is so arranged that, as the dancer roll changes position, the liquid shifts from one end of the container to the other end thereby changing the loading on the dancer roller. The Haley tension winding apparatus contemplates changing the loading on a dancer roll because of changes in the path of movement of the web, as the winding roll builds up, due to the geometry of the system. The tension control device of the Hank patent relies on liquid transfer from one container to another to correspondingly change the loading on a dancer roll.

SUMMARY OF THE INVENTION This invention relates to novel and useful web winding apparatus having improved operating characteristics. The invention pertains, in one of its specific aspects, to web winding apparatus having its parts so constructed and arranged as to effectively control web tension, as desired, from initiation of winding on an empty windup roll to completion of a full roll.

The web winding apparatus of this invention comprises a support, a pair of idler rolls, a dancer roll, a lay-on roll, and windup roll, and a drive for imparting rotation to the windup roll. The several rolls are carried by the support, are spaced apart and are rotatable about corresponding parallel axes. A web of a flexible material is adaptedto successively engage and pass over one of the idler rolls, under the dancer roll, over the other idler roll and partly around the lay-on roll and then engage and be wound on the windup roll. The apparatus also comprises first means connecting the dancer roll to the support and permitting bodily movement of that roll relative to and parallel to the windup roll, second means connecting the lay-on roll to the support and permitting bodily movement of that roll relative to and parallel to the windup roll, and a mechanism connected to and coacting with the first and second means for effecting programmed tension in the web during winding thereof on the windup roll. The mechanism includes variable fluid pressure means for applying corresponding force to the dancer roll through the first means and camming means for controlling operation of the fluidpressure means in response to bodily movement of the lay-on roll.

It is the primary object of this invention to provide web winding apparatus having improved structural features and operating characteristics.

Another object of this invention is to provide web winding apparatus including a dancer roll, a lay-on roll, a windup roll and a mechanism operatively associated with the dancer and lay-on rolls for programmed tensioning of a running web as the windup roll with wound web material increases in diameter.

Another object of this invention is to provide web winding apparatus for applying desired preset programmed tension in a web.

A further object of this invention is to provide apparatus of the character stated in the preceding object in which the programmed tension may be easily and quickly preset by the operator, as required.

This invention has for a still further object the provision of apparatus of the character indicated. which is sturdy and durable in construction; which is reasonable in manufacturing, installation and maintenance costs; which is adapted to be made in a wide range of sizes and adequately handle a variety of web materials; and which is capable of performing its intended functions in an entirely satisfactory manner over extended time periods.

The enumerated objects and additional objects, together with the advantages of the invention, will be readily apparent to persons trained in the art from the following detailed description and the accompanying drawings which describe and illustrate a preferred arrangement of web winding apparatus embodying the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings wherein like reference characters denote corresponding parts in the several views:

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG. 1 of the drawings, the therein il lustrated web winding apparatus comprises support means including a pair of spaced side frames 10, only one of which is shown in part. These frames carry a plurality of rolls, namely a first idler roll 11 having a shaft 12, a dancer roll 13 having a shaft 14, a second idler roll 15 having a shaft 16, a lay-on roll 17 having a shaft 18 and a windup or core roll 19 having a shaft 20. The axes of the several shafts are parallel and spaced apart. Shafts 12, 16 and 20 are mounted for rotation on the support means and their axes are stationary. Shafts 14 and 18 are mounted, as will be described, to permit bodily movement thereof and of the corresponding rolls.

Windup roll 19 is driven by an electric motor M-l. This motor has a rotary shaft 21 which is coaxial with and coupled to shaft 20 by a magnetic clutch 22.

A web of flexiblematerial W is adapted to travel as indicated by the arrows in FIG. 1 and engage and pass over idler roll 11, under dancer roll 13, over idler roll 15 over lay-on roll 17 and finally around windup roll 19 on which it forms a wound roll 23 of the material. The dancer roll rides in a loop 24 of the web. The height of this loop is variable depending on the force exerted by the dancer roll and the resulting tension applied to the web, as will be explained further along herein.

Dancer roll 13 is pivotal bodily relative to the support means through the medium of a first means 25 which will now be described. Means 25 includes a pivot shaft 26 which is parallel to dancer roll shaft 14 and is supported for rotation by frames 10. Secured to and pivotal with shaft 26 is a pair of spaced parallel arms 27. Shaft 14 is mounted for free rotation at an end of each arm 27, as indicated at 28. The portion of each arm to the side of shaft 26 remote from shaft 14 is equipped with a counterweight 29 for balancing the weight of the dancer roll.

Similarly, lay-on roll 17 is pivotal bodily relative to the support means and windup roll 19 through the medium of a second means 30. This means includes a pivot shaft 31 which is parallel to lay-on roll shaft 18 and is supported for rotation by frames 10. Each of a pair of spaced parallel arms 32 is secured at one end to shaft 31 and is rotatable therewith. Shaft 18 is mounted for free rotation at the other ends of arms 32, as indicated at 33. In the course of winding web W onto windup roll 19, lay-on roll 17 moves bodily upwardly through angle A (FIG. 1) from its broken line position, when the windup roll is empty, to its full line position, when wound roll 23 attains its required diameter.

The apparatus also comprises a mechanism, generally denoted by numeral 35, which is connected to and cooperates with first means 25 and second means 30, for effecting programmed tension in web W in the course of winding the web on windup roll 19. Mechanism 35 includes a third means 36 for exerting a variable force on arms 27 and, therefore, on dancer roll 13, and a fourth means 37 for controlling the operation of the third means in response to bodily movement oflay-on roll 17 about the axis ofshaft 31.

Third means 36 comprises a variable fluid pressure unit including a cylinder 38 mounted on the support means and a plunger 39 which is slidable through the lower end of the cylinder. The free end of plunger 39 is connected to a rod 40 which extends between and is secured to arms 27. The fluid pressure unit is preferably pneumatic. Air under predetermined pressure is admitted into the upper end of cylinder 38 by way of a conduit 41 and exerts a downward force to plunger 39. This causes clockwise pivotal movement of means 25 about the axis of shaft 26, as viewed in FIG. 1, and the application of corresponding force on dancer roll 13, thereby creating corresponding tension in web W.

The force exerted by the fluid pressure unit and the resultant force applied to the dancer roll and the tension created in web W is controlled by fourth means 37, which will now be described. This means includes an L-shaped lever 42 having a lateral arm 43 and a vertical arm 44. As is best shown in FIG. 3, lever 42 is mounted on and affixed to shaft 31 by a key 45 for rotation therewith. Lever arm 43 carries a reversible electric motor M-2 having a rotary shaft 46 which is connected to a threaded rod 47 by a universal coupling 48. A cam member 50, having an arcuate lower camming surface 51, is pivotally connected at one end to the lower end of arm 44 by a pivot pin 52. A block 53 is pivotally connected to the other end of cam member 50, as indicated at 54. Block 53 has a through tap for engagement with threaded rod 47. It will be evident from an examination of FIG. 3 that Motor M2 adjusts the effective length of threaded rod 47 and correspondingly adjusts or varies the position of cam member 50 relative to lever arm 44 about the axis of pin 52.

A generally L-shaped lever 55 is positioned substantially wholly below lever 42 and consists of an upstanding arm 56 and a lateral arm 57. The free end of arm 56 is pivotally connected to a side frame by a pin 58. A block 59 is pivotally connected to the free end of arm 57, as indicated at 60. This block has a through tap for engagement with a threaded rod 61. A second reversible electric motor M-3 is mounted on a support frame and has a rotary shaft 62 which is connected to threaded rod 61 by a universal coupling 63. Motor M-3 adjusts the effective length of threaded rod 61 and, therefore, the angular position of lever 55 about the axis ofpin 58.

Attached to'lever arm 56 is an air control valve 64 which includes a casing 65 and a reciprocable valve stem 66 that extends through and beyond the upper end of the casing. High pressure air from a convenient source of supply (not shown) is admitted to the inlet of valve 64 by a conduit 67 and is discharged and then transmitted from the outlet of the valve by a conduit 68 to conduit 41 and thence into the upper end of cylinder 38. Conduit 68 is equipped with a pressure gauge 69. Valve 64 is in the nature of a pressure regulating valve and may be of any suitable known construction wherein the pressure of the air discharged therefrom is dependent on the position of valve stem 66. A bracket 70 is affixed to the upper end of valve stem 66 and carries a pin 71 that is parallel to pin 52 and shaft 31. Mounted for rotation on pin 71 is a roller 72 which bears against camming surface 51.

When lay-on roll 17 is at its broken line position (FIG. 1), i.e., against empty windup roll 19, it is important that the angular position of lever 42 be such that the axes of shaft 31, pivot pin 52 and pivot pin 71 intersect a straight line which is denoted BB in FIG. 3. Also, for best results during operation, the axis of pivot pin 52 should be as close as practical to the periphery of roller 72 and the axis of pivot pin 58 should intersect a line C-C which is normal to line BB and passes through the line of contact between camming surface 51 and roller 72.

Reference is now had to FIG. 2 for an understanding of the electrical circuitry that is incorporated in the present invention. The circuitry includes a pair of terminals 73 for connection to a suitable source of alternating current supply (not shown), a pair of potentiometers 74 and 75 for controlling the line voltage to a rectifier 76 which supplies direct current to the coil 77 of magnetic clutch 22. The clutch is a slip type and the voltage applied to its coil controls the amount of torque transmitted by drive motor M-l to winding shaft 20, thereby controlling the rotational speed of windup roll 19. A pair of selector switches 78 and 79 control the operation of adjusting motors M-2 and M-3, respectively.

In describing the operation of the illustrated embodiment of the invention, it is assumed initially that cam 50 is so adjusted that it does not affect the position of roller 72 and, therefore, valve stem 66 as lever arm 44 pivots in a counterclockwise direction through the angle A (FIG. 3) in the course of winding the web from empty windup roll condition to full wound roll 23. Accordingly, constant pressure is applied to dancer roll 13 by fluid pressure means 36 throughout the winding cycle. The dancer roll controls the torque delivered by clutch 22 through the medium of potentiometer 74 which is actuated by shaft 26. As the diameter of the material being wound on the windup roll increases, its rotational speed will decrease to slightly less than the linear speed of web W entering over idler roll 11. This decrease in rotational speed is caused by insufficient delivered torque by the clutch since the winding torque requirement has increased due to increase in the torque arm radius of the web winding on the roll. The decrease in web speed will result in a downward movement of the dancer roll which results in an increase in excitation to the clutch to provide increased transmitted torque and a restoration of the correct web speed. These changes occur continuously and smoothly. Inasmuch as the web tension and, therefore, winding tension is directly proportional to the effective weight of the dancer roll, it will be observed that the foregoing will result in constant tension winding.

In order to obtain a taper tension, cam 50 is adjusted by motor M-2 to the position indicated by the broken lines in FIG. 3. Consequently and as the winding roll builds up in diameter with the web material and as lever arm 44 rotates through angle A, roller 72 and valve stem 66 move upwardly and gradually decrease the pressure of the air transmitted by valve 64 and conduits 68 and 41 to cylinder 38. This causes a corresponding decrease in the force exerted by plunger 39 upon means 25, thereby gradually decreasing the effective force exerted by the dancer roll on the web and correspondingly gradually decreasing the tension in the web as the winding roll increases in size.

One of the important advantages of this invention is the ease and simplicity of making adjustments for the initial winding tension and the amount of taper tension desired. The initial tension is obtained or-adjusted by first lowering lay-on roll 17 to rest on empty windup roll 19, as indicated by the dotted line position of roll 17 (FIG. 1). At this time, cam 50 is in the full line position shown in FIG. 3. Switch 79 is closed and motor M-3 is energized, thereby actuating valve stem 66 and roller 72 to the illustrated position and adjusting the air pressure that is delivered by conduits 68 and 41 to cylinder 38. This air pressure is read on gauge 69 which, if desired, may be calibrated to indicate tension directly and this reading will be the initial winding tension on the windup roll 19.

The apparatus is then set for final tension in the web by raising lay-on roll 17 to its full line position which corresponds to its position for a full wound roll 23. Lever 42 and cam 50 will now have rotated in a counterclockwise direction through angle A (FIG. 3). The cam is then raised or lowered, as required, by closing switch 78 and operating motor M-Z until the desired final tension is indicated on gauge 69.

It will be observed that, due to the straight line construction described earlier herein and the proximity of the axis of shaft pin 52 to the line of contact between cam surface 51 and roller 72, the setting of the initial tension will not be affected by any adjustment of the fina'l tension, thereby obviating any need for the operator to make further adjustments.

It has been found that a camming surface 51 having the configuration of a circular arc affords a satisfactory tension taper program in most instances. It should be borne in mind, however, that other camming surface configurations may be employed advantageously to obtain desired tension programming.

While a magnetic clutch 22 is preferred for coupling drive shaft 21 to windup roll shaft 20, any other suitable type of controllable slip clutch may be substituted therefor. In fact, the clutch may be eliminated by utilizing a variable speed drive motor which is controlled by the position of dancer roll 13.

As illustrated and described, first means 25 and second means 30, respectively, carry and permit bodily movement of dancer roll 13 and lay-on roll 17 about the axes of corresponding shaft 26 and 31. While this arrangement is preferred, it should be borne in mind that it is within the purview of this invention to permit requisite bodily movement of such rolls by utilizing means other than the indicated pivot shafts. For example, the dancer roll may be arranged for vertical sliding movement by using constructions of the character disclosed in Haley US. Pat. No. 2,847,210 and Sherman U.S. Pat. No. 3,2 l 8,2l9. 1

Based on the foregoing, it is believed that the construction, operation, objects and advantages of my present invention will be readily comprehended by persons skilled in the art, without further description. It is to be clearly understood, however, that various changes in the construction described above and illustrated in the drawings may be made without departing from the scope of the invention, it being intended that all matter contained in the description or shown in the drawings shall be interpreted as illustrative only and not in a limiting sense.

I claim:

1. Web winding apparatus comprising a support, a dancer roll, a lay-on roll, a wind-up roll, a drive for imparting rotation to the wind-up roll, said rolls being carried by the support, spaced apart and rotatable about corresponding parallel axes, a web of a flexible material being adapted to successively engage the dancer roll and the lay-on roll and then engage and be wound on the wind-up roll, first means connecting the dancer roll to the support and permitting bodily movement of the dancer roll while maintaining its axis parallel to the axes of the other rolls, second means connecting the lay-on roll to the support and permitting bodily movement of the lay-on roll relative to the wind-up roll while maintaining its axis parallel to the axes of the other rolls, and a mechanism connected to and coactin g with the first and second means for effecting programmed tension in the web during winding thereof on the wind-up roll, said mechanism comprising variable fluid pressure third means for applying corresponding force to the dancer roll through the first means.

2. Web winding apparatus according to claim 1 additionally comprising camrning fourth means for controlling the force applied by the third means in response to bodily movement of ble with the second means about a first pivotal axis, a cam carried by the lever, a pressure regulating valve having an inlet for connection to a source of high pressure fluid and an outlet communicating with the third means, said valve including a stem that is operatively associated with the cam for controlling the pressure of the fluid discharged from the valve in response to movement of the cam.

5. Web winding apparatus according to claim 2 wherein the third means comprises a cylinder for receiving fluid under pressure and a plunger extending through an end of the cylinder and connected to the first means, said plunger being slidable relative to the cylinder in response to variations in the pressure of the fluid, and wherein the fourth means comprises a first lever connected to and movable with the second means, a cam carried by the lever, a pressure regulating valve having an inlet for connection to a source of high pressure fluid and an outlet communicating with the cylinder, said valve including a reciprocable stem device that is operatively associated with the cam for controlling the pressure of the fluid discharged from the valve in response to movement of the cam.

6. Web winding apparatus according to claim 5 wherein the cam is connected and movable relative to the first lever about a second pivotal axis, means being provided to adjust the position of the cam relative to the first lever about said second pivotal axis.

7. Web winding apparatus according to claim 6 wherein the fourth means also comprises a second lever connected to and movable relative to the support about a third pivotal axis, said pressure regulating valve being mounted on the second lever, and means for adjusting the position of the lever relative to the support about said third pivotal axis.

8. Web winding apparatus according to claim 7 wherein the first and second axes intersect a substantially rectilinear line that is coincident with the longitudinal axis of the valve stem device when the parts are in such a relative position that the lay-on roll is disposed directly against the wind-up roll.

9. Web winding apparatus according to claim 8 wherein a straight line passing through the third axis and the region of engagement between the cam and the valve stem device is substantially normal to said rectilinear line.

10. Web winding apparatus according to claim 9 wherein the valve stem device includes a roller rotatable about a fourth axis that is parallel to and closely adjacent said second pivotal axis, said roller engaging the cam.

11. Web winding apparatus according to claim 10 wherein said first, second and fourth axes intersect a substantially rectilinear line when the parts are in such a relative position that the lay-on roll is disposed directly against the wind-up roll.

12. Web winding apparatus according to claim 11 wherein a straight line passing through said third pivotal axis and region of engagement between the cam and the roller is substantially normal to said rectilinear line.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated March 21, 1972 Patent No. 3, 650,490

- Inventor(s) Alan J. Saunders It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 36, i.e. claim 6, line 1, cancel "5" and v substitute 4 Signed and sealed this 1st day of August 1972.

(SEAL) Attest:

EDWARD M.FI.LETCHER,JR. ROBERT GOITSCHALK Attesting Officer- Commissioner of Patents USCOMMDC 60376-P69 U.S. GOVERNMENT PRINTING OFFICE: I959 0-365-334 FORM PO-1050 (10-69) 

1. Web winding apparatus comprising a support, a dancer roll, a lay-on roll, a wind-up roll, a drive for imparting rotation to the wind-up roll, said rolls being carried by the support, spaced apart and rotatable about corresponding parallel axes, a web of a flexible material being adapted to successively engage the dancer roll and the lay-on roll and then engage and be wound on the wind-up roll, first means connecting the dancer roll to the support and permitting bodily movement of the dancer roll while maintaining its axis parallel to the axes of the other rolls, second means connecting the lay-on roll to the support and permitting bodily movement of the lay-on roll relative to the wind-up roll while maintaining its axis parallel to the axes of the other rolls, and a mechanism connected to and coacting with the first and second means for effecting programmed tension in the web during winding thereof on the wind-up roll, said mechanism comprising variable fluid pressure third means for applying corresponding force to the dancer roll through the first means.
 2. Web winding apparatus according to claim 1 additionally comprising camming fourth means for controlling the force applied by the third means in response to bodily movement of the lay-on roll.
 3. Web winding apparatus according to claim 1 wherein the third means comprises a cylinder for receiving fluid under pressure and a plunger extending through an end of the cylinder and connected to the first means, said plunger being slidable relative to the cylinder in response to variations in the pressure of the fluid.
 4. Web winding apparatus according to claim 2 wherein the fourth means comprises a first lever connected to and movable with the second means about a first pivotal axis, a cam carried by the lever, a pressure regulating valve having an inlet for connection to a source of high pressure fluid and an outlet communicating with the third means, said valve including a stem that is operatively associated with the cam for controlling the pressure of the fluid discharged from the valve in response to movement of the cam.
 5. Web winding apparatus according to claim 2 wherein the third means comprises a cylinder for receiving fluid under pressure and a plunger extending through an end of the cylinder and connected to the first means, said plunger being slidable relative to the cylinder in response to variations in the pressure of the fluid, and wherein the fourth means comprises a first lever connected to and movable with the second means, a cam carried by the lever, a pressure regulating valve having an inlet for connection to a source of high pressure fluid and an outlet communicating with the cylinder, said valve including a reciprocable stem device that is operatively associated with the cam for coNtrolling the pressure of the fluid discharged from the valve in response to movement of the cam.
 6. Web winding apparatus according to claim 5 wherein the cam is connected and movable relative to the first lever about a second pivotal axis, means being provided to adjust the position of the cam relative to the first lever about said second pivotal axis.
 7. Web winding apparatus according to claim 6 wherein the fourth means also comprises a second lever connected to and movable relative to the support about a third pivotal axis, said pressure regulating valve being mounted on the second lever, and means for adjusting the position of the lever relative to the support about said third pivotal axis.
 8. Web winding apparatus according to claim 7 wherein the first and second axes intersect a substantially rectilinear line that is coincident with the longitudinal axis of the valve stem device when the parts are in such a relative position that the lay-on roll is disposed directly against the wind-up roll.
 9. Web winding apparatus according to claim 8 wherein a straight line passing through the third axis and the region of engagement between the cam and the valve stem device is substantially normal to said rectilinear line.
 10. Web winding apparatus according to claim 9 wherein the valve stem device includes a roller rotatable about a fourth axis that is parallel to and closely adjacent said second pivotal axis, said roller engaging the cam.
 11. Web winding apparatus according to claim 10 wherein said first, second and fourth axes intersect a substantially rectilinear line when the parts are in such a relative position that the lay-on roll is disposed directly against the wind-up roll.
 12. Web winding apparatus according to claim 11 wherein a straight line passing through said third pivotal axis and region of engagement between the cam and the roller is substantially normal to said rectilinear line. 